Charter Communications is suing a Los Angeles-based law firm, claiming its malpractice cost the cable operator and its holding companies more than $150 million in a cable acquisition.

The suit, filed April 6 in U.S. District Court for the Central District of California in Santa Ana, claims St. Louis-based Charter's legal counsel in the deal ' Irell & Manella LLP ' erred in legal preparations for a transaction in which Charter holding companies acquired Bresnan Communications systems from the Bresnan family and investors that included AT&T.

Bresnan owners were to get units in a Charter holding company, which could later be converted to Charter Communications stock or cash.